New-onset postpartum hypertension in women without a history of hypertensive disorders of pregnancy: a multicenter study in Japan

The aim of this study was to investigate the prevalence and risk factors of new-onset postpartum hypertension (PPHTN), defined as new-onset hypertension during the postpartum period, among women without a history of hypertension during pregnancy and labor. A multicenter retrospective study was conducted using clinical data of women who delivered at term between 2011 and 2018 at 12 maternity hospitals. A total of 18,295 normotensive women were eligible, after excluding those with hypertensive disorders of pregnancy or hypertension during labor. New-onset PPHTN was defined as multiple blood pressure readings of >_ 140/90 mmHg between 1 d and 4 weeks postpartum among normotensive women throughout pregnancy. Multivariate regression analyses were performed to evaluate the risk factors for new-onset PPHTN. Among the 18,295 normotensive women, 227 (1.2%) presented with new-onset PPHTN. The prevalence was higher in women who delivered via cesarean section than in those who delivered vaginally (7.0% and 1.0%, respectively). The independent risk factors were maternal age =35 years (adjusted odds ratio 1.67, 95% confidence interval [1.10-2.53]), nulliparity (1.83 [1.24-2.71]), high normal blood pressure (systolic blood pressure [SBP] 120-129 and diastolic blood pressure [DBP] < 80) at the last prenatal check-up (1.96 [1.23-3.13]), elevated blood pressure (SBP 130-139 and/or DBP 80-89) (6.42 [4.15-9.95]), urinary protein 1+ (1.99 [1.27-3.11]), scheduled cesarean section (4.05 [1.69-9.69]), and emergency cesarean section (10.02 [5.10-19.70]). New-onset PPHTN was observed in 1.2% of the normotensive women, with women who delivered via cesarean section having the highest risk. Close postpartum blood pressure monitoring may be required for women with multiple risk factors to identify new-onset PPHTN in a timely manner and reduce adverse maternal consequences.